This invention relates to a switchably controlled liquid sealed type vibration isolator used to support a power unit, such as an automobile engine in a vibration isolating manner.
A switchably controlled liquid sealed type vibration isolator adapted to switch vibration isolating characteristics thereof in accordance with two kinds of vibrations in different frequency regions, such as shaking vibration and idling vibration, has been proposed as a liquid sealed type vibration isolator for use as a mount for supporting a vibrating body, such as an automobile engine, etc. so as not to have the vibration of the vibrating body transmitted to a body of a vehicle.
For example, Japanese Patent Laid-Open No. 173372/1999 proposes a switchably controlled liquid sealed type vibration isolator including a metal fixing member on a side of a vibration source, an outer cylindrical metal member on a side of a support, a vibration isolating base member interposed between the two metal members and formed of an elastic rubber member, a first diaphragm fixed to the outer cylindrical metal member so as to be opposed to the vibration isolating base member, and a partition provided between the diaphragm and vibration isolating base member, the partition and vibration isolating base member defining a main liquid chamber therebetween, the partition and first diaphragm forming therebetween a first auxiliary liquid chamber communicating with the main liquid chamber via a first orifice, the partition being provided at a main liquid chamber-side portion thereof with a second auxiliary liquid chamber communicating with the main liquid chamber via a second orifice, and an atmospheric pressure and negative pressure changeover chamber separated from the second auxiliary chamber via a second diaphragm.
In this proposed liquid sealed type vibration isolator, the partition is formed of a main partition member defining the first orifice on an outer circumference thereof, and a partition plate member defining the second auxiliary chamber and orifice. The main partition member, to which the second diaphragm is fixed, forms the change-over chamber on the main liquid chamber-side portion and is fitted in an inner circumference of the outer cylindrical metal member. The partition plate member is fitted around the diaphragm to hold a circumferential edge portion thereof. Both the main partition member and partition plate member are installed held between a main liquid chamber-side surface of the vibration isolating base member and a liquid chamber-side stepped portion of the outer cylindrical metal member.
However, in the above-mentioned construction, the main partition member and partition plate member have to be installed submerged in a liquid in order by a press fitting method as orifice-communicating openings of both thereof are positioned. Therefore, the structure to be assembled is complicated, and, moreover, a high stability of the structure is rarely obtained due to variations in accuracy of other parts.
The main partition member and partition plate member are held between the vibration isolating base member and the liquid chamber-side stepped portion of the outer cylindrical metal member and thereby retained in a mere contacting state. Therefore, the predetermined functions become unable to be fulfilled due to changes with the lapse of time in the condition of the parts during the use of the vibration isolator in a vehicle-mounted state. Such changes are ascribed to the fluctuation of a liquid pressure caused by the vibration of the vibration isolating base member, or permanent set in fatigue and slip of the rubber portions between the parts caused by the heat. The changes thus cause the sealing to become insufficient, and the passages working as the orifices to be short-circuited.
The present invention has been made in view of these facts, and provides a switchably controlled liquid sealed type vibration isolator having a structure which permits an inner partition, by which an inner hollow space is divided into a main liquid chamber and two auxiliary liquid chambers, to be assembled tentatively in an air environment, plural constituent parts to be combined together reliably and easily without being dislocated, and, moreover, the relative displacement of the constituent parts which occurs due to changes with the lapse of time of themselves in a vehicle-mounted state to be reduced to a low level, whereby retention of an excellent sealed condition among the parts and the improvement of the durability of the same parts are attained.
The present invention provides a switchably controlled liquid sealed type vibration isolator including a vibration isolating base member formed of an elastic rubber member, a first metal fixing member combined with one of upper and lower portions of the vibration isolating base member, a main cylindrical metal member combined with the other portion of the vibration isolating base member, a first diaphragm fixed to the main metal member so as to be opposed to the vibration isolating base member, a partition provided between the vibration isolating base member and first diaphragm, a main liquid chamber formed between the partition and vibration isolating base member, a first auxiliary liquid chamber formed between the partition and first diaphragm, a second auxiliary liquid chamber formed on a main liquid chamber-side portion of the partition, a change-over chamber separated from the second auxiliary chamber via a second diaphragm and capable of receiving therein an atmospheric pressure and a negative pressure in a switchable manner, and first and second orifices communicating the main liquid chamber with the first and second auxiliary chambers respectively, the vibration isolator further having the following structure so as to solve the aforementioned problems.
The partition has at an outer circumferential portion thereof a main partition member forming the first orifice, and the second diaphragm is provided on a main liquid chamber side portion of the main partition member so as to form the change-over chamber in a diametrically inner portion thereof. A partition plate member pressing a circumferential portion of the second diaphragm toward the main partition member to form the second auxiliary liquid chamber between the partition plate member and the same diaphragm is engaged with and fitted firmly around an outer circumferential portion of the main partition member by a swaging device for this outer circumferential portion. A portion defined by the main partition member and partition plate member on an outer side of the second auxiliary liquid chamber is formed as the second orifice. A partition receiving plate having an outer circumferential edge portion extending outward beyond an outer end of the main partition member is fixed by a press fitting device with respect to the main partition member to the portion of the main partition member which is on the side of the first auxiliary liquid chamber. The partition plate member is fitted liquid-tightly in an inner circumferential portion of the main metal member, and the outer circumferential edge portion of the partition receiving plate is fixed with the first diaphragm to the main metal member by a swaging member.
According to the liquid-sealed type vibration isolator of-this construction, the structural parts of the partition incorporated in an inner portion thereof, i.e. the main partition member on an outer circumferential side of which the first orifice is formed, the second diaphragm forming the change-over chamber on the portion thereof which is on the side of the main liquid chamber, the partition plate member forming the second auxiliary chamber and orifice, and parts of the partition receiving plate can be combined together in the air initially with ease and separately from the main metal member without causing these members and parts to be dislocated. Therefore, after such a temporary combining operation, plural structural parts can be combined accurately by press fitting the partition plate member of the partition firmly into an inner circumference of the main metal member, and then swaging the outer circumferential portion of the partition receiving plate with the first diaphragm to the main metal member, whereby a liquid sealed type vibration isolator provided with two auxiliary liquid chambers, two orifices and two diaphragms can be assembled easily.
Especially, since the partition plate member pressing the second diaphragm to form the second auxiliary liquid chamber and orifice is fitted firmly in an engaged state around the outer circumference of the main partition member by a swaging device for the same outer circumference, the main partition member and the main partition plate member are combined with each other without a fear of their being separated from each other. This enables the second diaphragm to be pressed reliably, and can prevent an excessive decrease in the sealability of the parts and the short-circuiting of the passage as an orifice which are ascribed to changes with the lapse of time in the vibration isolating base member during the use thereof.
In this liquid sealed type vibration isolator, a second metal fixing member covering a space on the outer side of the first diaphragm is provided, which is swaged with the partition receiving plate and first diaphragm to the main metal member, and these parts can also be combined together easily just as the above-mentioned parts.
In the liquid sealed type vibration isolators of each of the above-described inventions, the main partition member is provided on the portion of an outer circumference thereof which is on the side of the first auxiliary liquid chamber with an orifice-forming recess, which are defined by the partition receiving plate and main metal member to form the first orifice. Therefore, the main partition member can be manufactured easily, and is suitable for practicing the vibration isolator.
The partition plate member is preferably formed by fitting firmly the outer circumferential portion thereof around the outer circumference of the portion of the main partition member which is on the side of the main liquid chamber, bending at least a part of a circumferential end portion of the partition plate member inward in the above-mentioned orifice-forming recess, and swaging this bent portion to the main partition member. This enables the partition plate member to be swaged by utilizing the orifice-forming recess.
The circumferential end portion of the partition plate member can be swaged at plural circumferentially spaced parts thereof to the main partition member, and also at substantially all parts of the circumference thereof to the same member.